The present invention relates to a guide bar for a chain saw, and more particularly to a guide bar which has a reduced weight.
Chain saws are used extensively in the logging industry. Since they must often be used in rough and remote terrain, it is important that the chain saw be as light in weight as possible, yet rugged and durable for the hard use it will encounter.
The chain saw generally will include a motor head, from the forward part of which extends an elongate, substantially planar guide bar, about which a saw chain is driven for cutting. Since the guide bar extends some distance forwardly of the motor head, its weight can produce a very tiring effect on a user. For this reason, it is desirable to provide as light a guide bar as possible.
In the past, efforts have been made to produce light weight guide bars. Such prior efforts have included bars with honeycomb or foam centers having outer metal laminates secured thereto, or providing a synthetic insert in an opening in the center of the bar. Since the materials used previously may not be as durable as metal and may be more expensive, they have not been as successful as desired.
It is an object of the present invention to provide an improved chain saw guide bar which has a reduced weight, yet which provides good durability and toughness for extended use.
Another object of the present invention is to provide a reduced weight guide bar for a chain saw which will function in a manner similar to prior guide bars, yet which will be sufficiently reduced in weight that it will provide greater ease of use for an operator.
More specifically, an object of the present invention is to provide a chain saw guide bar which has a main body portion having opposed side faces, a rear end, a forward end, elongate upper and lower edges providing a peripheral guide edge for guiding a loop of saw chain, and having an elongate opening extending laterally therethorough intermediate the rear and forward ends and the upper and lower edges, with the opening having opposed forward and rear ends and elongate upper and lower reaches. The main body portion is made from a first metal, such as high-grade steel. An elongate insert made from a second, lighter weight metal, such as aluminum, is configured to fit closely in the opening in the main body portion, with the insert having forward and rear end portions directed toward the forward and rear ends of the main body portion. The main body portion has a holding mechanism at an end of the opening for retaining an end portion of the insert to inhibit release of the end portion of the insert from the main body portion laterally of the main body portion.
A benefit of such construction is that the main body portion will have sufficient strength, durability, and toughness to support a saw chain driven thereabout for cutting, and the lighter weight metal insert provides weight reduction without adversely altering necessary operating characteristics of the saw bar.
A further object of the present invention is to provide a chain saw guide bar having a main body portion made of first metal material, an insert of a lighter weight second metal material disposed in an elongate opening in the main body portion, the main body portion having a socket formed at an end of the opening intermediate opposed side faces of the main body portion, and the insert having a protrusion extending longitudinally from remainder portions of the insert, which protrusion is received in the socket to inhibit release of the end portion of the insert from the main body portion laterally of the guide bar. With such structure, flexing of the guide bar during use will not result in the end of the insert releasing from the main body portion of the guide bar as might otherwise occur if the end portion of the insert were not so captured.
A still further object of the present invention is to provide a chain saw guide bar with a main body portion having an elongate opening formed therein with an insert of a lighter weight material configured to fit closely in the opening and be held therein, wherein the insert comprises a first insert section and a second insert section, each of which are substantially planar and are disposed in face-to-face contact with each other in the opening. The two insert sections together have a combined thickness which is no greater than the thickness of the main body portion, allowing the guide bar to have a reduced weight and still function to cut a kerf of a width no greater than that of which a usual saw bar would allow.
A still further object of the present invention is to provide such a guide bar having first and second insert sections in which each of the insert sections has a protrusion at its opposite ends which fit into sockets on the main body portion at opposite ends of the opening to hold opposite ends of the insert sections to the main body portion and inhibit release of the insert sections laterally from the main body portion.
Yet another object of the present invention is to provide a reduced weight chain saw guide bar wherein the first and second insert sections have contiguous inner faces which contact each other along a plane paralleling and disposed substantially centrally between opposed outer faces of the main body portion and the first and second insert sections are secured to each other.
A still further object of the present invention is to provide a novel method for producing a reduced weight chain saw guide bar having a main body portion with an elongate opening extending therethrough and an insert of a lighter weight material secured therein in such a manner that the insert is held firmly in the main body section.
These and other objects and advantages of the present invention will be apparent from the following detailed description of preferred embodiments thereof and from the attached drawings.